Melanoma is one kind of a skin cancer called malignant melanoma. As the skin cancer, there are various kinds, and melanoma is a skin cancer having very high malignancy. A cell producing a melanin pigment, which exists in cells constituting a skin, is called a pigment cell (melanocyte), and the cell which has been cancerated is melanoma.
The incident number of melanoma in Japan is estimated to be about 1.5 to 2 persons per a population of 100000 persons, and it is presumed that about 1500 to 2000 persons develop melanoma annually. In Europe and the United States, the incident number is said to be ten-some or more persons per a population of 100000, and in Australia, the incident number of twenty-some or more persons per a population of 100000 is reported, and it is said that this is the highest incident number in the world. Therefore, peoples in Europe and the United States, and Australia, particularly, a white race is concerned with melanoma, and pays an attention to incidence of melanoma. Both in foreign countries and Japan, a tendency is recognized that incidence of melanoma is increased year by year. According to the certain search, it is reported that the number of deceased persons in one year due to this disease in Japan amounts to around 450 persons.
Peoples at any age develop melanoma, and particularly, when peoples become 40 years old or older, the incidence rate is increased, and the incidence rate becomes highest in their 60s to 70s. The incidence rate of infants is very small, but it cannot be said that infants do not develop melanoma, and there is recently a tendency that incidence in youths at their 20s to 30s is increased. Regarding the gender, there is no tendency that melanoma is frequent in either of a man or a woman, and melanoma is developed in both of a man and a woman. In Japanese, a site at which melanoma is easily developed is planta (sole of foot) in most cases, and the planta accounts for about 30%. It is the characteristic in Japanese that melanoma is also developed frequently at a part of a nail of a foot and a finger. In addition, like European and American peoples, melanoma is developed in a skin at any site such as the body, hand, foot, face and head.
On the other hand, measurement of a serum tumor marker is important not only in diagnosis of melanoma, but also in early detection of recurrence in postoperative cases, and determination of the therapeutic effect of advanced stage cases. As a tumor marker of melanoma, previously, usefulness of LDH and 5-S-cysteinyldopa (5-S-CD) of serum has been known, and further more recently, an S-100β protein and melanoma inhibitory activity (MIA) have been reported as more sensitive markers.
In Japan, as the existing tumor marker, 5-S-CD is mainly used, but these previously used tumor markers become positive only in a considerably advanced tumor such as Stage IV, and it must be said that usefulness is limited in respect of early diagnosis of melanoma, and early detection of postoperative recurrence.
The present inventors have conducted research regarding usefulness of GPC3 (glypican-3) and SPARC (Secreted protein, acidic rich in cysteine; another name osteonectin or BM-40) as a tumor marker, and previously reported that GPC3 and a combination of GPC3 and SPARC can be useful as a tumor marker of melanoma (Patent Documents 1 and 2).
However, in the method using an antibody to GPC3 described in Patent Document 1, the positive ratio of a melanoma patient is around 40%, and also in the method using a combination of an antibody to GPC3 and an antibody to SPARC described in Patent Document 2, the positive ratio of a melanoma patient is around 60%, and there is still room for improving detection sensitivity.
Further, since quality of commercially available antibodies which are usually used in detection of these tumor markers is not stable, low reproducibility is also a problem.
In addition, in the present description and drawings, particularly, in Examples, a novel monoclonal antibody provided by the present invention is called as a “novel antibody”, and a method of the present invention using the novel antibody is called as a “novel method” in some cases. On the other hand, the commercially available anti-GPC3 antibody and anti-SPARC antibody which are usually used currently are called as a “commercially available antibody” in some cases. Further, serum LDH and 5-S-CD which have previously been used as the existing tumor marker are called as a “previous tumor marker” or an “existing tumor marker” in some cases. In addition, a method using these previous (existing) tumor markers is called as a “previous method” in some cases.